When to plant daffodils in Niigata: 20 November – end of December

Daffodil in Niigata: depth, winter cold, pests and pets

Plant daffodils three times the bulb’s height deep (RHS): about 13–15 cm for large bulbs, 15–20 cm apart (University of Georgia Extension). The RHS advises planting them early in autumn, ideally in September in the UK, so do not leave them late: aim for the start of the window, 20 November.

In Niigata the average daily temperature stays at 10 °C or lower for about 19 weeks a year (our estimate from ten years of monthly weather). For this bulb Wisconsin Horticulture Extension gives a cold period of 15–17 weeks at about 2–10 °C. The winter here gives that in the ground, so the bulbs need no pre-chilling.

Daffodils are long-lived: clumps slowly expand over the years (RHS). Leave the leaves for at least eight weeks after flowering — they feed next year’s flowers (University of Georgia Extension).

Squirrels avoid daffodils, so they can be planted among tulips to reduce losses (RHS). Daffodils are toxic to dogs, cats and horses; the bulbs are the most poisonous part, and a large amount can cause convulsions and heart rhythm problems (ASPCA).

Sources: RHS, University of Georgia Extension, Wisconsin Horticulture Extension, ASPCA.